The present application relates to electrical appliances and power supplies therefor.
Recent years have seen a proliferation of portable electrical appliances. Digital cameras, media players, mobile telephones, and global positioning system (GPS) devices are but a few examples of this trend. In many cases, these devices are provided with a power adapter that converts power from a power source such as an alternating current (AC) power line to a form used by the appliance.
Unfortunately, losses in the power adapter can degrade the energy efficiency of the system. This problem is exacerbated by the fact the power adapters are often left connected to the input power source for extended periods of time.
In the ubiquitous case of a mobile telephone, for example, the phone is connected to a power adapter, at which the point an onboard charger may enter an active charging mode in which the batteries are brought to a fully charged state. If the phone is not disconnected from the power adapter, the charger may enter a maintenance mode in which power from the adapter is used to maintain the battery state of charge. At some point, the mobile phone is typically disconnected from the adapter and used as desired. Nonetheless, the charger is often not unplugged from the power outlet.
Another trend has been an increased emphasis on energy efficiency. As result, manufactures have sought to improve the energy efficiency of their power adapters, for example by using relatively more efficient electrical components and circuit configurations such as switched mode power converters. In the U.S., these efforts have gained increasing visibility through the Energy Star® program promulgated by the U.S. Environmental Protection Agency. Those products that meet certain energy efficiency criteria may receive the Energy Star qualification and display the Energy Star certification mark. See, e.g., Energy Star Program Requirements for Products with Battery Charging Systems (Draft 2); Energy Star Program Requirements for Single Voltage External AC-DC and AC-AC Power Supplies (Draft 1.1).
Nonetheless, there remains room for improvement.